1. Field of the Invention
This invention relates to panels comprising transparent laminated windows or canopies for aircraft, aircraft window panels comprising canopies or windows, and an improved method of fabricating such panels. Laminated aircraft windows or canopies usually comprise alternate plies of a rigid, transparent glazing material, such as glass or various well-known substitutes for glass (such as polycarbonates, acrylic esters and polyesters) alternating with plies of a flexible interlayer material, such as polyurethanes, polyvinyl acetals and silicones. The peripheral portions of certain plies are offset from one another in laminated aircraft windows and the extended marginal portion of the larger ply or plies of flexible interlayer material is reinforced with one or more frame-shaped reinforcing members of a material that is difficult to bond to one or both of the plies flanking the major surfaces of the reinforcing member in the laminated window.
In fabricating laminated windows for aircraft, not only must the alternate plies of rigid and flexible materials be bonded to one another and to the reinforcing members with sufficient adhesive strength to enable the laminated window to preserve its unitary integrity during use at various ranges of temperatures and pressures, but it is also necessary for the laminated window to remain attached securely to the body of the aircraft in which it is installed. It is especially important that the laminated window and its attachment to the aircraft body be reinforced structurally to minimize the likelihood of the window separating from the body of the aircraft. It is also important that any adhesive component of an aircraft panel be easy to apply to facilitate its fabrication.
For the purpose of this disclosure, the term "window" is limited to a laminate of transparent window elements including marginally located opaque or transparent reinforcing members that are incorporated within the thickness of the window. The term "panel" includes the window together with exterior reinforcing elements that bear at least a portion of the load in attaching the window to the body of the aircraft.
2. Description of the Prior Art
U.S. Pat. No. 2,360,192 to Bestian discloses the use of a fabric or paper which is impregnated with a liquid solution of an adhesive for bonding different substances. The adhesive comprises the reaction product of an isocyanate with an alkylene imine.
The general concept of using an adhesive impregnated strip to bond diverse substances is also disclosed in U.S. Pat. No. 3,516,884 to Heeter; U.S. Pat. No. 3,533,877 to Cook and U.S. Pat. No. 3,424,642 to Orcutt. The Orcutt patent uses resin impregnated tapes for mechanically and chemically sealing various components of aircraft windows, and specifically discloses using reinforced thermosetting resin in the A stage and in the B stage. The panels comprising the windows and the resin impregnated tapes are assembled, and during lamination of the panels under heat and pressure, the resins set into the C stage to form a unitary part of the resulting aircraft panel.
U.S. Pat. No. 3,312,574 to Laur and U.S. Pat. No. 3,312,587 to Wilson are typical of many patents disclosing the use of silicone rubber interlayers for laminated glass windows.
U.S. Pat. No. 3,074,903 to Fincke discloses the use of silicone resin impregnated fabric to form fabric reinforced laminated structures. This patent does not suggest using the impregnated fabric as a means for bonding the laminated structure to a structure receiving body or member.
U.S. Pat. No. 3,306,800 to Pleuddemann discloses the concept of using a polyorganic bonding agent having attached silyl groups for bonding thermoplastic resin, such as polycarbonate, to inorganic materials, such as glass, steel, aluminum, etc. The Pleuddemann patent does not suggest using the silyl-group containing bonding agent in the form of a resin impregnated fabric or tape.
U.S. Pat. No. 3,332,817 to Obenhaus discloses using silicone impregnated mica paper for making mica paper capacitors. This patent contemplates laminating foil sheet electrodes and spaces of reconstituted mica paper impregnated with a partially cured silicone resin. The laminate is then subjected to heat and pressure to cure the resin in situ.